The internet does not appear to play a key role in radicalising people to al Qaida's cause, a Home Office report found.
Extremists' websites have often been thought to enable the terror group to reach hundreds of thousands of potential supporters and recruits.
But the internet fails to offer the personal attachments needed to radicalise someone, the assessment said.
The report on al Qaida-influenced radicalism (Aqir) found that membership of a social network containing at least one radicalised member was "one of the main factors linked to exposure to radicalising influence".
But the internet was not key, it said. "That the internet does not appear to play a significant role in Aqir might be surprising, given that it is the social networking medium par excellence," the report said.
"However, the fact that the technology presents obstacles to the formation of intimate bonds could explain this counter-intuitive finding. Personal attachments to radicalising agents, be they peers, recruiters or moral authority figures, play a prominent role in Aqir."
The report led to a more risk-based approach when targeting individuals, institutions and ideologies in the Government's new Prevent strategy, which seeks to stop people becoming terrorists or supporting terrorism.
It was one of three linked reports commissioned by the previous Labour government in 2009.
The researchers found there was no "vulnerability profile" to help identity those at risk of becoming radicalised without creating an "unmanageable number of false positives". But most were young, often aged between 15 and 35, unable to cope with stress or challenging situations, and have a weak commitment to conventional moral rules and values, it said.
A "turning point" or key event in someone's life can also be significant, such as the loss of a job or the wrongful death of a loved one. They added: "The key categories of causal factors are those that impact on people's vulnerability to radicalising moral contexts, their exposure to radicalising settings, and in the emergence of these radicalising settings."
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